Radio communications systems are increasingly being used for wireless mobile communications. An example of a radio communications system is a cellular phone network. Cellular radio communications systems are wide area communications networks which utilize a frequency (channel) reuse pattern. The design and operation of an analog cellular phone system is described in an article entitled Advanced Mobile Phone Service by Blecher, IEEE Transactions on Vehicular Technology, Vol. VT29, No. 2, May, 1980, pp. 238-244. The analog mobile cellular system is also referred to as the "AMPS" system.
Recently, digital cellular phone systems have also been proposed and implemented using a Time-Division Multiple Access (TDMA) architecture. Standards have also been set by the Electronics Industries Association (EIA) and the Telecommunications Industries Association (TIA) for an American Digital Cellular (ADC) architecture which is a dual mode analog and digital system following EIA/TIA document IS-54B. Telephones which implement the IS-54B dual mode architecture are presently being marketed by the assignee of the present invention. Different standards have been promulgated for digital cellular phone systems in Europe. The European digital cellular system, also referred to as GSM, also uses a TDMA architecture.
Proposals have recently been made to expand the cellular phone network into a radio personal communications system. The radio personal communications system provides mobile radio voice, digital, video and/or multimedia communications using radio personal communications terminals. Thus, any form of information may be sent and received. Radio personal communications terminals include a radio telephone, such as a cellular telephone, and may include other components for voice, digital, video and/or multimedia communications.
A radio personal communications system includes at least one telephone base station, also referred to herein as a "base station". A base station is a low power transceiver which communicates with a radio personal communications terminal such as a cellular telephone over a limited distance, such as tens of meters, and is also electrically connected to the conventional public wire telephone network. The base station allows the owner of a radio personal communications terminal to directly access the wire telephone network without passing through the cellular phone network, whose access rates are typically more costly. When located outside the range of the base station, the personal communications terminal automatically communicates with the cellular phone network at the prevailing access rates.
A major problem in implementing a radio personal communications system is security for communications between the base station and the personal communications terminal. Modern cellular telephone networks include security systems and methods to prevent eavesdropping and telephone fraud. Eavesdropping may be prevented by using encryption of radio transmissions between a cellular phone and a cellular network. Fraud may be prevented by preventing radio telephone transmissions between the cellular phone and the cellular network unless identification Information is successfully exchanged between the cellular phone and the cellular network. Existing cellular systems, such as the AMPS system, the ADC system, and the GSM system each include their own security systems and methods. Security should not be compromised by communications between the radio personal communications terminal and the base station of a radio personal communications system.